Polyarylates (aromatic polyesters) can be made by reacting an aromatic diacid with a diacetate of bisphenol, generally employing a two-stage reaction process in which a bisphenol is reacted with an acid or anhydride, such as acetic acid or acetic anhydride, followed by reaction of the resulting aliphatic carboxylic acid ester of the bisphenol with an aromatic diacid.
Problems persist in producing polyesters. Sublimation of reagents with losses of reagents out of the reaction vessel and/or deposition of reagents or of oligomers on reactor heads or in pipes, upsets the reaction stoichiometry and results in products of erratic inherent viscosity (I.V.), insufficient final molecular weight, discolored products, and other facets detracting from the commercial usefulness of the polymers.
A variety of solvents have been suggested in the prior art to assist in use of catalysts, or to reduce sublimation of reactants, and the like. Among these have been sulfolane, diphenyl acetone, benzophenone, N-methyl pyrrolidone, hexamethyl phosphoramide, benzonitrile, diethyl ether, triethylene glycol, diphenyl ether; cycloaliphatic, substituted aromatic compounds containing a benzylic and/or a tertiary hydrogen, such as diisopropylbenzene; biphenyl; and sulfones.
Nevertheless, still needed is a simple, effective, convenient, process to produce polyarylates, with little or no sublimation of reagents, and result in a product of good moldability, consistent suitable high inherent viscosity, and low color. Accordingly, such is the object of my invention.